1. Field of the Invention
The present invention relates to information recording and reproducing devices and methods which can be obtained with applied scanning probe microscope (hereinafter abbreviated SPM) technologies.
2. Description of the Related Art
In recent years, super high density recording methods obtained with applied SPM technologies including scanning tunnel microscopes (hereinafter abbreviated STM) or atomic force microscopes (hereinafter abbreviated AFM) have been proposed. There are many known methods to change the contour of the surface of the recording medium or to change physical properties of the surface of the recording medium by SPM, such as the mechanical processing method of pressing a probe to the recording medium directly, the electrical field evaporation method of depositing probe material onto the surface of the recording medium or eliminating a material from the surface of the recording medium by generating a strong electric field between the probe and the substrate. Any of these recording methods may achieve a super high recording density of greater than 1 Tbit/inch.sup.2.
In general, such conventional information recording and reproducing technologies have shortcomings in terms of processing stability. For example, when the electrical field evaporation method is used, a comparatively high voltage should be applied between the probe and the recording medium to generate the electric field necessary to change the surface state of the recording medium or the probe. However,when a high voltage is applied between the probe and the recording medium, it is possible that the tip of the probe will be deformed or the probe may break when recording information on the recording medium. For that reason, a stable information recording is not accomplished by these methods.
A method to solve the above-mentioned problem of the electrical field evaporation method is proposed in the article of "Appl. Phys. Lett., Vol. 61, No. 8, Aug. 24, 1992, pp. 1003-1005". The method is to change the shape of PMMA surface by heating a probe which contacts the recording medium by a laser beam. Since this method uses thermal energy from the probe to record information on the recording medium, it is not necessary to apply voltage between the probe and the recording medium and it is possible to extend the life of the probe. However, in this method, the information recording speed is rate-determined by the probe's heating speed and cooling speed and is limited to about 100 kHz.